ASP.NET: Putting App_Code Folder in Sub Directory

My website runs on old classic ASP code. I need an ASP.NET/VB application to run in only one sub directory. I put a web.config file in the sub directory and now ASP.NET/VB code works in that directory. My application requires a "library.vb" file to be inside the "App_Code" directory. Normally this would go inside the website's root directory but I only want it to apply to this sub directory. Is there something I could put in the web.config file so that it would look in the a sub-sub directory?